1. Field of the Invention
The present invention relates generally to a fuel supply system that supplies fuel stored in a fuel tank to an internal combustion engine, and more particularly to a fuel supply system provided with a connector joining device. The connector joining device includes an electric connector and another electric connector (coupler). The electric connector is disposed on a covering member for covering an opening of a fuel tank, and the another electric connector accommodates a lead wire connected to a terminal of the electric connector.
2. Description of Related Art
Conventionally, an in-tank type fuel supply system having a pump module that is accommodated in a fuel tank is widely known (see, for example, JP-A-2008-196440). The fuel supply system includes a covering member, a subtank, and a pump module. The covering member closes an opening of the fuel tank formed at an upper wall part thereof. The subtank is disposed in the fuel tank. The pump module is accommodated in the subtank. The pump module includes a fuel pump and a fuel filter. The fuel pump suctions and then discharges fuel after pressurizing it, and the fuel filter is disposed to surround the fuel pump in an outer peripheral direction thereof. An electric connector is provided for the covering member so as to project from a lower surface of the covering member in a direction of gravitational force thereof toward the subtank. This electric connector is connected to another electric connector (coupler).
A connector joining device, which connects the electric connector disposed on the covering member that covers the opening of the fuel tank and the electric connector (coupler) as its counterpart, may have the following three constitutions. The connector joining device with the first constitution may include an electric connector including a first housing and an electric connector (coupler) including a second housing. A recess having two male terminals together is formed on the first housing, and a projection that is to be fitted into the recess of the first housing is formed on the second housing. In this connector joining device, the two male terminals that coexist in the recess and two female terminals accommodated in the projection are connected.
The connector joining device with the second constitution may include an electric connector including a first housing and an electric connector (coupler) including a second housing. A recess that has an independent space for each male terminal to limit creepage surface leakage current is formed on the first housing. A projection that is to be fitted into the recess is formed for each female terminal on the second housing. The connector joining device with the third constitution may include an electric connector including a first housing, an electric connector (coupler) including a second housing, a first sealing member, and a second sealing member. A recess having two male terminals together is formed on the first housing, and a projection that is to be fitted into the recess of the first housing is formed on the second housing. The first sealing member seals the two female terminals accommodated in the projection from the subtank side, and the second sealing member seals a clearance formed between the recess and the projection.
Flaws in the conventional technology will be described below. Lately, from the viewpoint of environmental protection, some attempts have been made to use biological alcohol such as ethanol, mixed with gasoline. Alcohol blended fuel in which gasoline and alcohol are mixed at a given rate, or ethanol 100 percent fuel has high conductivity compared to conventional fuel such as gasoline. Therefore, when voltage is applied between the two male terminals which coexist in the recess formed on the first housing of the electric connector (between a positive terminal and a negative terminal), electric current leaks easily between the positive terminal and the negative terminal with the alcohol blended fuel or the ethanol 100 percent fuel serving as a medium of the leakage.
Particularly, if the positive terminal and the negative terminal coexist in the single recess formed on the first housing of the electric connector, a current path is formed via the alcohol blended fuel or the ethanol 100 percent fuel which has entered into the first housing along a bottom surface of the recess. As a result, electrochemical corrosion (electrolytic corrosion) is caused in both the terminals and eventually, break in electric continuity between each terminal of the electric connector and each terminal of the electric connector (coupler), or breakage is generated in the terminals. Such electrolytic corrosion is more easily produced as a distance between both the terminals which coexist in the recess on the first housing of the electric connector is shorter. However, simply by making large the distance between both the terminals, the connector joining device grows in size and accordingly, upsizing of the fuel supply system disposed in the fuel tank is caused. In the conventional fuel supply system, each terminal is constantly immersed in (exposed to) fresh fuel only with the effect of limiting the creepage surface leakage current, and fuel in the connector joining device circulates by vibration of a vehicle. Consequently, the electrolytic corrosion of each terminal of the electric connector and each terminal of the electric connector (coupler) becomes advanced, so that electric conduction between each terminal of the electric connector and each terminal of the electric connector (coupler) may not be kept normal. Furthermore, although a perfect water proof connector prevents the entering of fuel into each terminal of the electric connector and each terminal of the electric connector (coupler), respiratory effect is not produced because it is sealed, and thereby fuel may enter into the water proof connector due to a pressure difference. In addition, once fuel has entered, the fuel never drains out, so that the electrolytic corrosion of each terminal of the electric connector and each terminal of the electric connector (coupler) is caused.